Issue #8237 has been updated by henry.maddocks (Henry Maddocks).


wardrop (Tom Wardrop) wrote:
> =begin
> The primary purpose of this proposal is to avoid unnecessary temporary variable assignment and extra expressions. This was good enough justification for the introduction of #tap, so perhaps it's a good enough reason to be considering this proposal. 
> =end

Object#tap wasn't introduced to avoid unnecessary temporary variable assignments. #tap is an implementation of the K combinator which has lots of uses beyond avoiding unnecessary temporaries. Also it was just an addition of a new method NOT a change to the language.

----------------------------------------
Feature #8237: Logical method chaining via inferred receiver
https://bugs.ruby-lang.org/issues/8237#change-38948

Author: wardrop (Tom Wardrop)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


=begin
This is a feature suggestion that was raised while discussing issue #8191. The feature suggestion is to introduce some form of logical method chaining to address this reasonably common pattern:

    user && user.profile && user.profile.website && user.profile.website.thumbnail

It would be reasonably trivial to shorten this to:

    user && .profile && .website && .thumbnail

The implementation I propose would be for Ruby to allow an inferred receiver; the dot prefix would be the syntax for this. The inferred receiver would resolve to the result of the last expression in the current scope. For illustrative purposes, the following would work under this proposal:

    "some string"
    puts .upcase #=> SOME STRING

Another example:

    puts .upcase if obj.success_message || obj.error_message

    # Instead of...

    message = (obj.success_message || obj.error_message)
    puts message.upcase if message

This can also potentially provide an alternative option in syntactically awkward scenario's, such as dealing with the return value of an if statement or a catch block, avoiding the need for temporary variable assignment:

    catch :halt do
      # Do something
    end

    if .nil?
       log.info "Request was halted" 
       response.body = "Sorry, but your request could not be completed"
    end

The logical chaining scenario is the main use case however. I just wanted to demonstrate how the proposed implementation could also be used in other creative ways.

=end


-- 
http://bugs.ruby-lang.org/